1. Field of the Invention
This invention relates to a terrestrial magnetic sensor and, more particularly, to a terrestrial magnetic sensor for detecting a terrestrial magnetism with a simple structure.
2. Description of the Prior Art
Heretofore, in a terrestrial magnetic sensor of this type, a magnetic core has been fixed with resin or the like.
Since the magnetic core has been fixed with resin or the like in the above-mentioned conventional terrestrial magnetic sensor, the sensor has a drawback that its magnetic permeability decreases to 50% or less of the initial magnetic permeability.
There is another drawback that the magnetic permeability of the magnetic core is affected by the influence of the variations in an environmental temperature.
Further, the conventional sensor has still another drawback that the magnetic core is affected by the influence of an external stress.